A later hygiene idle-timeout write can replace an aux-model cooldown on
the shared column. Drop the in-memory timer on that refresh so the
in-agent compressor is not still blocked after the DB row is hygiene.
Session hygiene persists compression_failure_cooldown_until after a
30s no-progress watchdog so the pre-agent pass can skip. The
in-conversation compressor read the same column and then refused to
run even though its own budget is sufficient.
Ignore hygiene idle-timeout errors on the in-agent path. Real
aux-model faults such as rate limits still block.
Fixes#86972